Method and apparatus for providing channel error protection for a source coded bit stream

Abstract

Unequal channel error protection is provided for a bit stream, e.g., a progressive source coded bit stream, by puncturing of a channel code. The channel code has a specified rate associated with a corresponding level of error protection, and is used to code a first portion of the bit stream. The channel code is subsequently punctured for at least a second portion of the bit stream so as to provide a rate higher than that of the designated rate. Commencement of the puncturing is deliberately delayed by an amount determined based at least in part on a memory of the channel code. Advantageously, the delay prevents propagation of errors in a channel decoder used to decode the channel coded bit stream. The progressive bit stream may be a progressive source coded video or audio bit stream, any other type of progressive information bit stream, or a partitioned source coded bit stream.

What is claimed is:  
     
       1. A method for providing channel error protection for a bit stream, the method comprising the steps of: 
       channel coding at least a first portion of the bit stream utilizing a channel code having a specified rate associated with a corresponding level of error protection; and  
       puncturing the channel code having the specified rate for at least a second portion of the bit stream so as to provide a rate higher than that of the designated rate, wherein commencement of the puncturing step is delayed by an amount determined based at least in part on a memory of the channel code, the delay preventing propagation of errors in a channel decoder used to decode the channel coded bit stream.  
     
     
       2. The method of  claim 1  wherein the channel code comprises a convolutional code. 
     
     
       3. The method of  claim 1  wherein the bit stream comprises a progressive source coded bit stream. 
     
     
       4. The method of  claim 3  wherein the progressive source coded bit stream comprises a progressive source coded video bit stream. 
     
     
       5. The method of  claim 3  wherein the progressive source coded bit stream comprises a progressive source coded audio bit stream. 
     
     
       6. The method of  claim 1  wherein the bit stream comprises a partitioned source coded bit stream. 
     
     
       7. The method of  claim 1  wherein the channel code is terminated only after all bits in a current frame of the bit stream are channel coded. 
     
     
       8. The method of  claim 1  wherein the amount of delay is greater than or equal to a memory of the channel code. 
     
     
       9. The method of  claim 1  wherein the amount of delay is less than or equal to a decoding depth of the channel decoder. 
     
     
       10. The method of  claim 1  wherein the amount of delay comprises a specified number of bits of the bit stream. 
     
     
       11. The method of  claim 1  wherein different amounts of delay are provided for puncturing of each of at least a subset of N classes of bits of the bit stream. 
     
     
       12. The method of  claim 1  further including the step of decoding the channel coded bit stream continuously from a most important bit of the bit stream to a least important bit of the bit stream. 
     
     
       13. An apparatus for providing channel error protection for a bit stream, the apparatus comprising: 
       a processor-based device operative to code at least a first portion of the bit stream utilizing a channel code having a specified rate associated with a corresponding level of error protection, the processor-base device being further operative to puncture the channel code having the specified rate for at least a second portion of the bit stream so as to provide a rate higher than that of the designated rate, wherein commencement of the puncturing is delayed by an amount determined based at least in part on a memory of the channel code, the delay preventing propagation of errors in a channel decoder used to decode the channel coded bit stream.  
     
     
       14. The apparatus of  claim 13  wherein the channel code comprises a convolutional code. 
     
     
       15. The apparatus of  claim 13  wherein the bit stream comprises a progressive source coded bit stream. 
     
     
       16. The apparatus of  claim 15  wherein the progressive source coded bit stream comprises a progressive source coded video bit stream. 
     
     
       17. The apparatus of  claim 15  wherein the progressive source coded bit stream comprises a progressive source coded audio bit stream. 
     
     
       18. The apparatus of  claim 13  wherein the bit stream comprises a partitioned source coded bit stream. 
     
     
       19. The apparatus of  claim 13  wherein the channel code is terminated only after all bits in a current frame of the bit stream are channel coded. 
     
     
       20. The apparatus of  claim 13  wherein the amount of delay is greater than or equal to a memory of the channel code. 
     
     
       21. The apparatus of  claim 13  wherein the amount of delay is less than or equal to a decoding depth of the channel decoder. 
     
     
       22. The apparatus of  claim 13  wherein the amount of delay comprises a specified number of bits of the bit stream. 
     
     
       23. The apparatus of  claim 13  wherein different amounts of delay are provided for puncturing of each of at least a subset of N classes of bits of the bit stream. 
     
     
       24. The apparatus of  claim 13  wherein the channel coded bit stream is decoded continuously from a most important bit of the bit stream to a least important bit of the bit stream. 
     
     
       25. An article of manufacture comprising a storage medium for storing one or more software programs for use in providing channel error protection for a bit stream, wherein the one or more programs when executed implement the steps of: 
       channel coding at least a first portion of the bit stream utilizing a channel code having a specified rate associated with a corresponding level of error protection; and  
       puncturing the channel code having the specified rate for at least a second portion of the bit stream so as to provide a rate higher than that of the designated rate, wherein commencement of the puncturing step is delayed by an amount determined based at least in part on a memory of the channel code, the delay preventing propagation of errors in a channel decoder used to decode the channel coded bit stream.